The 17-50 2.8 is going to be much faster due to being 2.8 across the spectrum so with this faster speed you get faster center point focusing (lens focus at 2.8 instead of 5.6 like the 15-85), the ability to blow your background out more if you want to do that, much much better low light usage, and much easier to use as it's a non variable aperture lens which makes working with flash way easier and shooting in general much easier.

So no sir, it is not just my opinion, it is fact.

Well yes, your points might be correct (having owned the non VC Tamron I know for a fact the AF is slower, and IIR it does not have full time manaul focus) but you conviently miss out the fact that the 15-85 has IS, it has a better IS than the 17-55, and this makes it better for hand held video (my expeiccnes, not just reading it on line) it is wider and longer. The long end not much difference but 2mm does make a difference (again, something ive found useful on many occasions). Just though few points might make a diffesome to some.

So your facts are almost right, but leaving out points to prove something doesn't actually prove anything.

Your points seem to be biased towards just one or two features, and while these might be relevant to you not everyone will need those at the loss of other features.